A short put means that you have the obligation to purchase the underlying at the strike price of the contract or $90 in your example. If assigned, your cost basis is $90 less the premium received ($2.75) or $87.25
If the purpose of selling the put is to acquire the stock at $87.25 then there's nothing to do. Either the put expires and you keep $2.75 or you are assigned and you acquire your position.
If you are selling premium for the sake of premium, then if the stock drops and heads toward $90, you can adjust the position and roll the short put down and possibly out in time. It's good practice to sell time for intrinsic value and note that it should be done before the option gets a fair amount in-the-money.
For example, XYZ approaches $90 some time from now. You've achieved a fair amount of time decay but premium has increased due to share price drop. Suppose your short put now trades for $3.50. Let's say that you can roll your short put down to $87.50 for at least break even. Now, your assignment price is $87.50 and your cost basis if assigned will be $84.75. Try to stay ahead of the tsunami (note the 35% market drop in March).
Use combo orders to roll options so that you can reduce slippage. IOW, place a vertical spread order to Buy To Close your current short $90 put and to Sell To Open the $87.50 put.
If your are indeed selling short puts for the sake of the premium rather than a desire to own the stock, consider selling credit spreads rather than short puts. This is an unforgiving market and owning some risk mitigation tends to be a wise decision.